I. Field of Invention
This invention relates generally to systems and methods of activating hydraulic cylinders on waste collection vehicles. More particularly, our invention relates to an improved hydraulic system and method for lifting and loading waste materials into waste collection vehicles.
II. Discussion of the Prior Art
A conventional refuse collection vehicle includes a cab, a body for storing refuse positioned at the rear of the cab, and a container-handling mechanism, (such as a lift arm or boom connected to a container gripper), carried on a wheeled chassis adjacent either the cab or the body. With an automated vehicle, the container-handling mechanism is typically controllably actuated by pressurized fluid selectively directed by controls located at the operator's compartment within the cab. Conventionally, the container-handling mechanism includes pivoting forks or opposed gripping members carried at the end of the lifting arm(s) or boom which is extendable and retractable relative to the curb or pick-up side of the vehicle. When the vehicle is brought to a stop, the lifting arm(s) and the associated fork(s) or gripping members engage the container. The container is then elevated through coordinated movement of the lifting arm(s) and/or boom and forks, for example, to position the container adjacent or over a hopper located behind the cab to deposit the refuse. Typically, these refuse collection vehicles are controlled by a sophisticated computer system utilizing logic circuits.
Lifting and loading mechanisms that engage containers in the front of the waste collection vehicles, known as "front end loaders," are in common use. (Throughout this application, "front" or "forward" will be used to signify the cab-end of the vehicle while "back" or "rearward" will denote the opposite direction of the vehicle.) These mechanisms conventionally have two curved arms that clear the cab in front of the vehicle, connected to a pair of pivoting forks or other articulating member that fit into side or bottom pockets of a steel collection container. Other conventional mechanisms employ a triangular frame in front of the cab that locks into a triangular pocket on the rear face of a collection container. An example of a prior art front-end loader is described and illustrated in U.S. Pat. No. 5,954,470 to Duell et al. Other types of collection containers can be used, as well. Another example of a lifting assembly is shown in U.S. Pat. No. 4,715,767 to Edelhoff et. al. Edelhoff discloses a lift arm arranged to pick-up the containers along the side of the cab, generically known as a "sideloader."
Waste collection vehicles are routinely used for collecting and transporting waste and recyclable materials discarded at both residential and commercial locations. The ubiquitous nature of these collection vehicles can negatively affect the reputation of companies that operate them and irritate the residential customers served by them. A major source of this irritation is the constant and repeated increased in noise level as the various hydraulic mechanisms on the vehicle are activated as the vehicle completes its route. Universally, waste collection vehicles use hydraulic systems to operate the lifting, dumping and compaction mechanisms. Operation of these hydraulic systems typically requires throttle advancement resulting in increased engine RPM, which translates into increased vehicle noise heard by those persons in proximity to the vehicle.
To waste collection companies operating waste collection vehicles, a key criterion is route time. The longer it takes to complete the route, the more expensive the operation. Timesavings on the order of minutes can have an enormous impact on operation costs. Moreover, approximately 50% of the route time is a result of operating the hydraulic systems on conventional waste collection vehicles. An improved hydraulic system and method of operation that would shorten the operation and route times would be a significant advantage in terms of time and expense. Likewise, the ability to operate hydraulic systems without the normally required increase in engine RPM would greatly reduce noise pollution, reduce fuel consumption and reduce air pollution. Our invention accomplishes these, as well as other goals.
Accordingly, one objective of our invention is to provide a method of activating hydraulic cylinders on waste collection vehicles that is more energy and time efficient.
Another object of the present invention is to provide an improved hydraulic system that replaces the conventional gear pump and open center valve with a close center value and a variable displacement pump.
Yet another object of the invention is to provide a more reliable and efficient waste collection vehicle that requires less maintenance at reduced operation costs. Another object is to provide an energy efficient method of cycling and emptying a refuse container using a front-end loader waste collection vehicle.
Still another object of our invention is to provide a method of cycling and emptying a refuse container without increasing engine RPM and that allows continuous and rapid movement of the refuse container throughout the cycle without the spillage normally associated with prior art methods.
Still other objects will be recognized upon reading the following disclosure.